Refining material for iron and steel and method of producing same



3,107,995 REFENWG MATERIAL FOR IIRQN AND TEEL AND METHOD OF PRGDUCHNG SAME Sampei Katakura, 117 Sanya-cho, Meguro-hu; Eienhichi Tachiki, 6 S-chome, Gotanda Shinagawa-ltu; and

Masarni Sate, 17 Z-chorne, Kaminalrazato Kita-iru, ail

of Tokyo, Japan No Drawing. Filed Dec. 18, 1961, Ser. No. 160,344

Claims priority, application Japan Apr. 6, 1961 13 Claims. (Cl. 7557) This invention relates to new refining material for iron and steel and to a method for producing said refining material. It relates more particularly to refining material of this type which is characterized in that it contains about 15 to about 65% by weight of chromium, about 3 to 35% by weight of calcium, 1 to about 8% by weight of copper, to about 8% by weight of strontium, and about to about 70% by weight of iron, and also con tains a maximum of about 2% by weight of carbon, silicon, aluminum, manganese, etc. as impurities.

The object of this invention is the embodiment of refining material to be added during the refining process of steel and cast iron so as to improve the qualities of the steel and cast iron.

Deoxidizing agents have heretofore been used for such purpose, for instance, aluminum, silicon, manganese, titanium, vanadium or calcium. These materials are intended to be used essentially for the separation of oxygen, and in addition they have separational effects for nitrogen, sulphur, phosphorus and carbon, although they have a differential action in this regard. Accordingly, when they are used either singly or in the form of a mixture or alloy of more than two of them, deoxidizing, denitriding and/ or desulfurizing is efiected. Chromium, on the other hand, is an element which, according to general recognition in the art, is greatly to be avoided in ordinary steel or cast iron. For instance, chromium contained in steel exists in the form of carbide and exerts an unfavor-- able influence on elongation characteristics. Chromium in cast iron is also a carbide-forming element; hence it holds the carbon in combined state and change of structure can not be expected even with the aid of heat treatment. More particularly, the said carbide prevents casting in thin form.

In spite of these contrary indications and expectations, it has been found according to the present invention that these defects can be entirely eliminated, and that the chromium remaining in the product is only (till-0.02% by weight, irrespective of the amount of chromium added, when the latter is added to a molten bath of iron or steel together with calcium. According to the present invention, it has been assured that a part of the chromium reacts with oxygen in the iron or steel and is eliminated as slag, the remainder being transformed into a new form having an entirely different molecular structure from that of usual chromium, as shown by X-ray analysis. Furthermore, electron microphotography demonstrates that such new form of the substance forms a crystalline ternary compound with calcium and carbon and disperses in the r on or steel. Such a compound is difiicult to dissolve in acid, and is so hard that it constitutes an important and decisive factor in determining the hardness of the material refined by the present refining material.-

According to the present invention, therefore, chromium which has heretofore been avoided in the refining 3f steel and cast iron has now become an important addilion component. In this way, chromium in association with calcium renders an important effect; however, it is not possible to add these substances individually to a molten bath of iron or steel because calcium is quite combustible so that the synergistic effect of the invention can I not thus be achieved. Nor can this disadvantage be eliminated in practice by the expedient of using these sub stances in the form of a simple alloy thereof, since the conventional alloying of calcium and chromium is quite difficult. The disadvantage is however obviated by the present invention, according to which a stable alloy is obtained through the special expedient that copper is added to inhibit the evaporation of calcium and subsequently the substance is added to iron to produce, with the chromium, an alloy of four elements. Such alloy can achieve the desired object; it is possible, if desired, to improve the solubility of the alloy in e.g. a molten bath of steel by adding thereto a small quantity of strontium. As a result of these expedients according to the instant invention, new refining material which is easily melted in a molten bath of iron or steel is readily produced, containing both calcium and chromium.

'In order that the present alloy may fulfill the desired object, it is preferable that its content of calcium and of chromium be as high as possible. However, the range of the alloying chromium may be from 15% to 65% by weight, and that of the calcium from 3% to 35% by weight. The amount of copper necessary ranges from 1 to about 8% by Weight, while the strontium can be included in an amount up to 20% by weight but is preferably less than about 8%, the remaining iron being 10 to about 70% by weight.

In order to obtain the optimum alloy according to the invention, each individual component is introduced into a crucible and the mixture subjected to melting. From the economic point of view, it is advantageous to use an iron-chromium alloy instead of chromium per se; Similarly, it is possible to use the calcium in the form of either an alloy with copper or with both copper and strontium. The strontium may also be used in the form of an alloy with calcium or with calcium-copper alloy.

In alloying the present substances, raw materials used are advantageously as follows: as iron, ordinary steel material is used; as chromium, 97-99% Cr is used or in the case of iron-chromium alloy, that with a chromium content of 65%; while as calcium, the product obtained either by an electrolytic or reducing process is used. Moreover, as copper, electrolytic copper is used. As the melting device, use is advantageously made of conventional apparatus which can be evacuated or filled with an inert gas atmosphere such as argon; and the alloying process is carried out at a temperature of 1300 to 1800 C.

The present alloy thus manufactured has a strong lustre of white silver, and its hardness is substantially high, ranging from to 250 Brinell according to the component ratio, and at the same time it is comparatively fragile and its solubility in a molten bath of steel or cast iron is quite good.

Furthermore, in order to accelerate the dissolution speed, it is sometimes desirable to alioy at a comparatively low temperature such as for example in the range from 800 to 1300 C. The alloy produced according to this method is somewhat dull, though substantially white silver-like as that of the preceding example; however, it is far easier to crush'such alloy. The alloy obtained according to the first process may be added to a molten bath of steel or cast iron at a temperature of 1500 to 1600 C., while that produced according to the latter process at somewhat low temperature may be added to the molten bath of steel or cast iron at a temperature of 1300 to 1500 C.

The following example illustrates a presently method of carrying the invention into effect.

An alumina crucible or a magnesia crucible inside which a vacuum may be produced is set in a high-frequency elecpreferred Patented Get. 22, 1%53.

oneness 3 tric furnace. Crushed iron, chromium, copper, or an ironchromium alloy is mixed with calcium and strontium which have been fined in the atmosphere of an inert gas such as argon. The crucible is charged with the mixture which is then heated up to a temperature in a range of 800 to 1800 C. in vacuo or in the atmosphere of an inert gas so as to sinter or melt the mixture and to alloy it. In case an alloy of calcium and strontium or an alloy of one of these with copper is used, the operation is similar to the above. Typical mixtures are shown in the following Table I:

lhese impurities comprise carbon, silicon, aluminum, manganese e.

In using the present material for iron, steel or cast iron the plunging temperature and holding time may vary appreciably according to the molten iron or steel, the respective optimum ranges being from 1400-1650 C. and from 2 to 15 minutes.

The results obtained when mixture A is added to steel or cast iron having different carbon contents is shown below:

(1) In case of iron and steel.- kilograms of electrolytic iron having a carbon content of 0.00l0.002% is subjected to melting in a high frequency furnace, and subsequently the mixture A is added at a temperature of 1600 C. in the ratios of 3/1000, 4/1000 and 5/1000, respectively, holding for ten minutes, followed by 2/ 1000 of aluminum. The oxygen, nitrogen and hydrogen contents in the steel are shown :by the following analytical Although the nitrogen and hydrogen contents are substantially the same as when ordinary deoxidizing agent is used, the oxygen content is greaterthan two or more times the amount present when deoxidizing with aluminum alone.

The starting iron is rather pure iron and its carbon content is quite low so that the amount of oxygen removed is comparatively small, the xygen after the addition of refining material being increased. Thus, it is noteworthy that a considerable quantity of oxygen is present. In spite thereof, the quantity of iron oxide and/ or oxides of other non-ferrous metallic impurities is small and the structure is quite ferritic, thus not exhibiting any unusual structure due to the considerable amount of oxygen present. Furthermore, the elongation is over 40% so that it is -15% higher than that of steel prepared with other deoxidizing agents. Therefore, the steel has the same working properties as that obtained with addition of 0.3% manganese, although here no manganese is added at all. Such phenomenon is not observable at all during the steeling process so that it can be assumed that the large amount of theabove-rnentioned oxygen is not in the ordinary form of FeO; moreover, as shown in Table H the oxygen content differs according to the added amount of the refining material according to the invention. From tion, is contained in the iron in unusual combination.

That is to say, it is considered that a novel iron compound containing oxygen and hydrogen is produced, through chemical reactions. It is to this novel compound to which the enhanced elongation and toughness characteristics of the iron may be ascribed. It is moreover con sidered that the reason why steel material treated with the present refining material has increased anti-corrosion properties as compared with steel material not treated with the present refining material is due to such compound. The fact that the present refining material exhibits a prominent improving effect on steel which could not have been expected from the ordinary refining or deoxidizing agent is ascribed to this point, which is why the new additament of this inventon is not regarded merely as an addition agent but rather as refining material for iron and steel.

The above-mentioned increasing phenomenon of the contained oxygen occurs markedly in case the carbon content is low, but such phenomenondecreases rapidly according to increase in carbon content. For instance, in ordinary steel material having a carbon content of 0.10 to 0.20%, such phenomenon decreases to /3, while in steel material having a carbon content of 0.35 to 0.40%, it decreases to to /8. Ratio of oxygen of the new compound to the remaining oxygen in these various kinds of steels is to if the carbon content is extremely low, and it reaches 70% even in steel having a carbon content of 0.35 to 0.40%.

When the carbon content is 3%, more or less, as in cast iron, the residual oxygen is quite low so that the above-rnentioned phenomenon decreases to A A In this case, the ratio of oxygen in the new compound is very low.

(2) In case of cast iron.When the present refining material A is added to ordinary cast iron at 1500" C. in a ratio of 3/1000, holding eight minutes, the qualities of oxygen and nitrogen in the cast iron show the following analytical values:

' Table III Nitrogen, percent Oxygen,

lVithout addition After addition Cast articles after addition of the present refining material have a strong decarburizing tendency according to the added amount of the refining material, and at the same time hold the carbon in combined state and show high hardness. An example is given as follows:

Table IV Chromium Hardness, HBN

Man- Carbon Silicon gancse Copper Without addition.-. 3. 20 After addition 2.80

down of steel plate can be increased so that steel plate of deep necking down can be obtained. Furthermore, said efiects in carbon steel are quite remarkable in special steel, and are especially prominent in refractory steel. Moreover, this refining material increases the hardness and toughness not only of cast iron and malleable cast iron, but also of chilled cast iron.

Percentages throughout this example are by weight, except of course as regards elongation data.

Although additions of about 3 to about 5 parts per 1000 parts by weight of material being refined is exemplified (as the preferred range), the range may very well extend from 2 to 8 parts by weight.

What is claimed is:

1. Refining material for iron and steel, consisting of an alloy of chromium, calcium, copper and iron wherein the percentages of the ingredients of the alloy correspond to the following:

Percent by weight Chromium 15 to 65 Calcium 3 to 35 Copper 1 to about 8 Strontium 0 to about 8 Iron -10 to about 70 and a maximum of about 2% by weight of carbon, silicon, aluminum and manganese as impurities.

2. Refining material for iron and steel consisting of an alloy of:

Percent by weight Chromium 55.2

Calcium 13.5 Copper 2.7 Strontium 1.2 Iron 25.3 Impurities 2.1

3. Refining material for iron and steel consisting of an alloy of:

Percent by weight Chromium 37.5 Calcium 34.7

Copper p 8.2 Strontium 2.5

Iron 15.8 Impurities 1.3

4. Refining material for iron and steel consisting of an alloy of:

Percent by weight 6. Refining material for iron and steel consisting of an alloy of:

Percent by weight Chromium 25 .2 Calcium 15.3 Copper 3.1 Iron 55.8 Impurities 0.6

Percent by weight Chromium 15 to Calcium 3 to 35 Copper 1 to about 8 Strontium 0 to about 8 Iron 10 to about and a maximum of about 2% by weight of carbon, silicon, aluminum and manganese as impurities.

8. The method of enhancing the properties of iron and steel which consists of incorporating therein-to, in molten state and per 1000 parts thereof by Weight, 2 to 8 parts by weight of refining material according to claim 2.

9. The method of enhancing the properties of iron and steel which consists of incorporating thereinto, in molten state and per 1000 parts thereof by Weight, 2 to 8 parts by weight of refining material according to claim 3.

10. The method of enhancing the properties of iron and steel which consists of incorporating thereinto, in molten state and per 1000 parts thereof by weight, 2 to 8 parts by weight of refining material according to claim 4.

11. The method of enhancing the properties of iron and steel which, consists of incorporating thereinto, in molten state and per 1000 parts thereof by weight, 2 to 8 parts by Weight of refining material according to claim 5.

12. The method of enhancing the properties of iron and steel which consists of incorporating thereinto, in molten state and per 1000 parts thereof by weight, 2 to 8 parts by weight of refining material according to claim 6.

13. The method according to claim 7 wherein the refining material is incorporated in an amount of from 3 to 5 parts per 1000 parts by weight of material being refined.

References Cited in the file of this patent UNITED STATES PATENTS 2,086,098 Smalley July 6, 1937 2,580,171 Hagglund Dec. 25, 1951 3,031,297 Baranow Apr. 24, 1962 

1. REFINING MATERIAL FOR IRON AND STEEL, CONSISTING OF AN ALLOY OF CHROMIUM, CALCIUM, COPPER AND IRON WHEREIN THE PERCENTAGES OF THE INGREDIENTS OF THE ALLOY CORRESPOND TO THE FOLLOWING: 